Process for preparing thiolsulfonic acid esters



. 3,153,078. PROCESS FOR PREPARlNG THIOLSULFONIC ACE) ESTER William L. Fierce and Roger L. Weichinan, Crystal Lake,

. Ill, assignors to The Pure Oil Company, Chicago, 1111.,

a corporation of Ohio No Drawing. Filed Feb. 28, 1962, Ser. No. 176,432 12 Claims. (Cl. 266-453) This invention relates to new and useful improvements in processes for the preparation of alkanethiolsulfonic acid esters and more particularly to a process in which an organic disulfide is oxidized with nitrogen dioxide at a temperature of about 20-50 C. in the absence of other oxidizers.

While the thiolsulfonic acids, RSO' SH, are unknown, the salts and esters of these acidshave been prepared.

Considerable work has been devoted to the determination of the structure of the esters of the thiolsulfonic acids.

The structures RSOCOR. and RSO SR were both considered as possibilities. However, there is now general agreement that the structure RSO' SR is the correct one. See

- a E. E. Reid, Organic Chemistry of Bivalent Sulfur. This that can be used are hydrogen peroxide, perbenzoic acid, ozone, and 40% nitric acid. However, with other oxidizing agents the oxidation is incomplete in some cases and in other cases does not stop with the formation of the ester but proceeds further to produce more highly oxygenated derivatives. For example, electrolytic oxidation gives 'the sulfonic acid as the product. Chromate and permanganate oxidation sometimes produce sulfonic acids and sometimes the disulfones, RSO SO R. Gaseous oxygen, containing a catalytic amount of nitrogen oxides, oxidizes the disulfide to a mixture of the sulfonic acid and the disulfone, see U.S. Patent 2,433,395.

It is therefore one object of this invention to provide 'a new and improved process for the preparation of thiolsulfonic acid esters from organic disulfides.

Another object of this invention is the provision of an improved'process for the preparation of thiolsulfonic acid esters by oxidation of organic disulfides which is more selective for the'formation of thiolsulfonic acid esters than for the formation of other more highly oxygenated derivatives.

A feature of this invention is the provision of a process 'in which organic disulfides of the formula RSSR', where R and R are selected from the group consisting of alkyl and aralkyl radicals, are reacted with nitrogen dioxide at a temperature of about 20-50 C., in the absence of other oxidizers.

Other objects and features of this invention will become United States Patent alkyl and aralkyl radicals. We have found that this process must be carried out in the temperature range from about 20 to about 50 (3., preferably at about 40 C., and that higher or lower reaction temperatures result in the formation of substantial amounts of undesired higher oxidation products.

In carrying out the process, no catalyst is required and while the reaction can be carried out in the absence of a solvent, it is preferred to use an inert solvent which does not react with either the reactants or the products. Solvents which can be used include halogenated hydrocarbons such as carbon tetrachloride and chloroform, aromatic hydrocarbons such as benzene and toluene,

lower alkanes and cycloalkanes such as hexane, heptane.

and cyclohexane, etc., lower aliphatic ethers such as diethyl ether, tetrahydrofuran and dioxane', and lower alioxidizing agent can be recovered and reused. The byapparent from time to time throughout the specification and claims as hereinafter related.

This invention comprises a new process which we have discovered for oxidation of organic disulfides to the corresponding thiolsulfonic acid esters which is superior to and more selective than many previously known processes. In our process, the disulfide of the formula RSSR', preferably dissolved in an inert solvent, is oxidized to the product nitric oxide leaves the reaction Zone as a gas inert to the reactants or products andcan readily be reoxidized to nitrogen dioxide by oxygen and recycled to the reactor.

In carrying out this process it is preferred to use a ratio of nitrogen dioxide to organic disulfide ranging from stoichiometric up to about 10 times stoichiometric, i.e., from about 2:1 to about 20:1. The organic disulfides which are used in this process are preferably symmetrical disulfides although unsymmetrical disulfides can be used. When unsymmetrical disulfides are used in the reaction, the product obtained. contains esters of the composition RSO SR' and RSO SR. Organic disulfides which can be used in this process include dimethyl disulfide, diethyl disulfide, dipropyl disulfide, dibutyl disulfide, dipentyl disulfide, dihexyl disulfide, dioctyl disulfide, didecyl disulfide, dioctadecyl disulfide, dibenzyl disulfide, di(phenylethyl) disulfide, di(phenylpropyl) disulfide, methylethyl disulfide, methylpropyl disulfide, ethylpropyl disulfide, methylbenzyl disulfide, etc. The thiolsulfonic acid esters which are produced from these compounds in accordance withthis invention are useful for a variety of purposes. Some of the esters have bactericidal and fungicidal activity while others are useful as selective solvents-for the extraction of polycyclic aromatics and organic sulfur compounds from petroleum fractions.

The following non-limiting examples are illustrative of the scope of this invention.

EXAMPLE I the first 3 /2 hours of the run the N0 was completely absorbed. During the last one-half hour the characteristic brown color of N0 gas appeared in the efiluent gas from the reactor. After the run, the liquid contained a small amount of white solid and was dark, orange-brown corresponding thiolsulfonate ester by nitrogen dioxide in color. The liquid was allowed to standexposed to the air for a period of 14 hours to permit evolution of absorbed nitrogen dioxide. The reaction therefore consisted of an initial reaction period at 3l2 C. and a final reaction period of 14 hours at room temperature. The product was then washed 6 times with -ml. portions of water. All washes, including the last, were quite acidic. The final product, after drying over calcium chloride, was a clear, light yellow liquid. Distillation gave 12.8 g. of a water-White liquid. This liquid was analyzed for constituent elements and found to contain: S 43.2%, C 32.4%, H 6.7%, which corresponds to ethyl ethanethiolsulfonate, theoretical composition S 41.5%, C 31.1%, and H 6.6%. The ethyl ethanethiolsulfonate was obtained in this run in a yield of about 33.8%.

EXAMPLE II 4 'uid product was then separated by distilaltion into two fractions. The major fraction contained ethyl ethanethiolsulfonate in a yield of 362%, based on diethyl disulfide charged. The minor fraction consisted mainly of more highly oxygenated derivatives of diethyl disulfide.

EXAMPLE III In another experiment a 500-ml. flask was charged with 200 ml. carbon tetrachloride and 30.0 g. diethyl disulfide. The solution was stirred and heated by a hotwater bath to a temperature which varied from about 35 to 43 C. Nitrogen dioxide and nitrogen were bubbled through the liquid until N had been added in a mole ratio of 2.83 per mole of diethyl disulfide. The reaction product was filtered and distilled into two fractions. The major fraction consisted of ethyl ethanethiolsulfonate in a yield of about 54.7%, as determined by elemental analysis and molecular weight of the product.

EXAMPLE IV In still another experiment, the procedure followed in Example III was repeated except that the reaction mixture was heated to a temperature of 80 C. throughout the reaction time. In this reaction 32.2 g. nitrogen dioxide were added to 30.0 g. diethyl disulfide. There was no ethyl ethanethiolsulfonate formed after a four-hour reaction period. The product of this reaction was analyzed and found to consist mainly of one or more highly oxygenated derivatives of diethyl disulfide.

EXAMPLE V In still another experiment the procedure described in Examples III and IV was repeated except that the reaction mixture was cooled with an icewater bath to a reaction temperature in the range from about 4 to 8 C. In

Y 4 this experiment 29.0 g. nitrogen dioxide were added to 30.0 g. of diethyl disulfide. At the end of the four-hour reaction period, no ethyl ethanethiolsulfonate had formed. The product was analyzed and found to consist mainly of one or more highly oxygenated derivatives of diethyl disulfide.

EXAMPLE VI In still another experiment, the procedure described in Example V was followed except that the reaction mixture was maintained at a temperature ranging from 9 to +3 C. At the end of a four-hour reaction period, no ethyl ethanethiolsulfonate had formed. The liquid prodduct was analyzed and found to comprise a mixture of higher oxygenated derivatives of diethyl disulfide.

EXAMPLE VII Two additional runs were carried out in which a gaseous mixture of oxygen (100 cc./min.) and a small amount of nitric oxide (10 cc./min.) which would react in situ to form nitrogen dioxide, was bubbled through a solution of 30 g. of diethyl disulfide in carbon tetrachloride. One of the runs was carried out in a temperature range of 4- 16 C. and the other run at a temperature of 34-41 C. The first run was carried out for a period of 160 minutes and the second for a period of 175 minutes, followed by a 30-minute purge with nitrogen and fractional distillation. No ethyl ethanethiolsulfonate was formed in either run. However, the yield of the higher oxygenated products, possibly diethyl disulfone or ethane sulfonic anhydride, was higher than in any of the other experiments.

EXAMPLE VIII In another experiment, 60.4 g. dibenzyl disulfide and 54.4 g. nitrogen dioxide were reacted in solution in carbon tetrachloride for a period of 6.5 hours followed by an additional reaction period of 18 hours at room tempera ture. In this experiment, the corresponding thiolsulfonate was formed in a yield of about 36%. A similar run was carried out using diphenyl disulfide as the starting reactant and none of the thiolsulfonate was formed. When diphenyl disulfide was used as the reactant, an unidentified product was obtained.

EXAMPLE IX When this process is repeated using other solvents and other alkyl and aralkyl disulfides, the corresponding thiolsulfonate esters are formed, provided that the temperature is maintained in the range from about 20 to 50 C. At lower temperatures or at higher temperatures the product obtained consists mainly of more highly oxygenated derivatives such as the sulfone, or the sulfonic anhydride. In Table I there are shown typical reaction conditions and the products which are obtained when other disulfides and other solvents are used in carrying out this reaction.

Table l RSSR'+2NO RSO SRH-ZNO NOz/RSSR' Reaction Disulfide ratio Solvent Tgnp Product CHsSSCHa 2. 5 CHaSOzSCHa CzHsSSCHs--- 4.0 C2H5SO2S CH CzHsSSOzCHa C4H SSC4H9.. 3. O 40 C4H9SO2SC4HB CgHnSSCsHn 2. 5 40 'CsHnSOzSCaHn CH3SSC2H5 2. 1 50 CHaSOzSCzHnCHaSSOzCzHs C(iHEjCHZSSCHQCfi 6. O CuHsCHzSOfiCHzCaHg, CHaSSCHzCsIELs 10. O CzH5O C2115 40 CHaSOzSCHzCaHmCHSSOzGHzCsHr l C 0H7CHzSSUH2C uH7 3. O CH3CIC4HB 40 CiuH7CH2SOzSCHzCmH1 /CH2CH2 CzH5SSC2H5 20 O\ 0.... 2O CzHsSOzSCzHa CHaCHz From the foregoing examples, it is seen that the process which we have discovered is selective for the formation of thiolsulfonate esters in the temperature range from about 20 to about 50 C. In carrying out this process,

nitrogen dioxide is reacted with a dialkyl disulfide or a diarylalkyl disulfide, preferably in solution in an inert solvent, at the specified range of temperature. Under these reaction conditions, the thiolsulfonate ester is obtained in good yield. At lower temperatures or at higher 'with special emphasis upon several preferred embodiments of the invention. We Wish it to be understood that Within the scope of the appended claims this invention may be practiced otherwise than as specifically described herein.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A method of preparing thiolsulfonic acid esters of the formula RS SR' which comprises reacting a disulilde of the formula RSSR', Where R and R are selected from the group consisting of alkyl and aralkyl radicals, with nitrogen dioxide, 'as the sole oxidizer, at a temperature of about 50 C. in the absence of a catalyst.

2. A method in accordance with claim 1 in'which the reaction is carried out in an inert solvent.

3. A method in accordance With claim 1 in which the reaction is carried out-at a NO /RSSR' mol ratio in the range from about 2:1 to about 20:1.

4. A method in accordance with claim 1 in which the disulfide reactant is symmetrical.

but.

6. A method in accordance with claim 1 in which the disulfide reactant is dimethyl disulfide.

7. A method in accordance with claim 1 in which the disuliide reactant is diethyl disulfide.

8. A method in accordance with claim 1 in which the disulfide reactant is dioctyl disulfide.

9. A method in accordance with claim 1 in which the disulfide reactant is dibenzyl disulfide.

10. A method in accordance with claim 1 in which the disulfide reactant is methyl benzyl disulfide.

11. A method of preparing ethyl ethanethiolsulfonate which comprises reacting diethyl disulfide with gaseous nitrogen dioxide, as arsole oxidizer, in solution in carbon tetrachloride at a temperature of about C. in the absence of a catalyst.

References Cited in the file of this patent UNITED STATES PATENTS 2,433,395 Proell et a. Dec. 30, 1947 2,664,385 Wolff et al Dec. 29, 1953 2,925,442 Koheen et al. Feb. 16, 1960 2,935,532 Hubenett et a1. May 3, 1960 OTHER REFERENCES Remy: Treatise on Inorganic Chemistry, vol. 1, pages 593-594 (1956), Q.D. 151 R L E.

' Kharasch: Organic Sulfur Compounds, vol. I, pages 69, 458 (1961), QB. 412 S l 07.

E. E. Reid: Organic Chemistry of Bivalent Sulfur,

' v01. 1: pp. 330-4 1958 QLD. 412.5 1 4. 

1. A METHOD OF PREPARING THIOLSULFONIC ACID ESTERS OF THE FORMULA RSO2SO'' WHICH COMPRISES REACTING A DISULFIDE OF THE FORMULA RSSR'', WHERE R AND R'' ARE SELECTED FROM THE GROUP CONSISTING OF ALKYL AND ARALKYL RADICALS, WITH NITROGEN DIOXIDE, AS THE SOLE OXIDIZER, AT A TEMPERATURE OF ABOUT 20*-50*C. IN THE ABSENCE OF A CATALYST. 